The Interface of Tone and Morphology in Yoruba: A Harmonic Serialism Analysis

The interface of tone and morphology in Yoruba presents one of the most complex and theoretically productive sites in the formal phonology of African languages, where tonal alternations triggered by morphological operations challenge standard models of the morphology-phonology interface. This dissertation develops a comprehensive harmonic serialism analysis of the tone-morphology interface in Yoruba, making an original theoretical contribution by demonstrating that a constraint-based serial derivational model outperforms both standard Optimality Theory and rule-based approaches in accounting for Yoruba morpho-tonal phenomena. The empirical scope includes tonal alternations in nominal derivation, verb conjugation, compounding, and clause-level tonal sandhi triggered by morphological constituency. Data were collected through systematic elicitation of morpho-tonal paradigms from 50 native speakers in Oyo and Osun States and supplemented by acoustic phonetic analysis of tonal scaling in morphologically complex environments. The theoretical framework is grounded in Prince and Smolensky's Optimality Theory, McCarthy's harmonic serialism extension, and Pulleyblank's underspecification-based approach to Yoruba tonal phonology. Existing analyses of Yoruba morpho-tonal phenomena have been conducted within either standard OT or rule-based frameworks without systematic comparative evaluation of the harmonic serialism alternative. This dissertation fills that theoretical comparative gap with an original comprehensive empirical and formal analysis. Findings will demonstrate that harmonic serialism correctly predicts intermediate derivational stages in tonal alternation sequences that standard OT cannot capture. Keywords: tone-morphology interface, Yoruba, harmonic serialism, Optimality Theory, morpho-tonal phonology.